1. Field of the Invention
The present invention relates to a right-left driving force controller and, more particularly, to a technique for controlling right and left driving forces that maintain stable vehicle behavior.
2. Description of the Related Art
There has already been developed a right-left driving force distributor that controls yawing moment acting on a vehicle by producing a difference in driving force of a left wheel and driving force of a right wheel during turning of the vehicle, thereby enhancing turning performance of the vehicle.
However, the right-left driving force distributor of the related-art produces a difference between the right and left wheels in terms of driving force and confronts a problem of being incapable of preventing occurrence of slippages in the right and left wheels during straight ahead driving of the vehicle, and the like.
JP-A-2008-298191 describes a right-left driving force distributor having right-left driving force adjustment means and differential limitation means.
As described in connection with JP-A-2008-298191, the right-left driving force distributor having the right-left driving force adjustment means equipped with the differential limitation means requires control operation for selecting a proper one from the right-left driving force adjustment means and the differential limitation means depending on a situation.
A generally-conceived control technique is to compute, from a driving state of the vehicle, a right-left driving force adjustment level generated by the right-left driving force adjustment means and a differential limit level generated by the differential limitation means, thereby separately controlling the respective means.
However, such a technique has a potential of the right-left driving force adjustment means and the differential limitation means being simultaneously used. If the right-left driving force adjustment means and the differential limitation means are simultaneously used, torque interference will be induced by interlocking action, which raises a problem of deterioration of operating efficiency or controllability of the right-left driving force distributor.
In order to prevent such simultaneous use of the means, a technique for performing selective switching to solely one of the right-left driving force adjustment means and the differential limitation means is also conceivable. However, an abrupt change may arise in the driving force difference because of a difference between the right-left driving force adjustment level and the differential limit level at the time of switching between the right-left driving force adjustment means and the differential limitation means, which in turn makes the behavior of the vehicle discontiguous.